1. Field of the Invention
The invention relates to norbornyl-substituted silanes and the use thereof.
2. Background Art
Typical protecting group silanes such as TBM2-silane (tert-butyldimethylchlorosilane) or IPM2-silane (isopropyldimethylchlorosilane) are prepared by adding Grignard reagents to the corresponding chlorosilanes, and the remaining hydrogen is subsequently exchanged with HCl using a suitable catalyst, for example as disclosed in German patent DE-C 199 19 152: 
Organolithium reagents are also commonly used, for example as disclosed by E. J. Corey et al., J. AM. CHEM. SOC. 1972, 94, 6190-6191. Owing to their importance as protecting groups in organic synthesis, see, for example M. Lalonde et al., SYNTHESIS 1985, 817-845, a wide range is commercially available. However, the typical common protecting group silanes such as TBM2 and IPM2 bearing sterically demanding secondary or tertiary alkyl radicals, require expensive organometallic reagents for their preparation.
Owing to the regioselectivity of hydrosilylation, such compounds cannot be obtained directly from the corresponding alkenes, for example 2-methylprop-1-ene for TBM2 and propene for IPM2 by hydrosilylation of the latter with dimethylchlorosilane. The addition takes place preferably at the less sterically demanding carbon atom of the double bond, and so in the case of propene, leads to 1-propyl-dimethylchlorosilane and not to 2-propyl-dimethylchlorosilane, K. Szabo et al., HELV. CHIM. ACTA 1984, 67, 2128-2142.
The hydrosilylation of dimethylchlorosilane using norbornene under Pt catalysis leads preferably to exo-2-(dimethylchlorosilyl)bicyclo[2.2.1]heptane. See, e.g., V. J. Eddy et al., J. ORG. CHEM. 1987, 52(10), 1903-1906; and M. Green et al., J. CHEM. SOC. Dalton Trans. 1977, 1519-1525. This compound may also be referred to as norbornyldimethylchlorosilane (NM2-silane). Since norbornene is a disubstituted alkene, secondary alkyl radicals on silicon are thus accessible. Owing to the angle strain of norbornene, the reaction proceeds with considerably greater ease in comparison to other internal alkenes such as cyclopentene. The hydrosilylation of substituted norbornene derivatives using dimethylchlorosilane is likewise known. G. K. -I. Magomedov et al., J. GEN. CHEM. USSR (Engl. Transl.) 1988, 58(1), 91-93.
Dichlotosilanes which carry two bulky radicals such as isopropyl or tert-butyl likewise find use as protecting groups, in particular for diols (see, for example M. Lalonde, T. H. Chan, Synthesis 1985, 817-845). To prepare these compounds, organometallic reagents such as Grignard compounds are again used in a similar manner to the reaction scheme discussed previously.
Mononorbornyl-substituted dichlorosilanes are likewise known. For instance, the Pt catalyzed hydrosilylation of dichloromethylsilane using norbornene has been described which delivers the desired dichloronorbornylmethylsilane in 85% yield. M. Green et al., J. CHEM. SOC. Dalton Trans. 1977, 1519-1525).